In China, Shanxi Province, Shaanxi Province, Inner Mongolia, Ningxia Province, and Gansu Province constitute an energy “Golden Triangle” region. The coal resource of the energy “Golden Triangle” region is characterized by shallow depth of embedment, thin bedrock, and thick coal seam, etc. In 2011, the coal production of this area reached 2.382 billion tons, accounting for 67.7% of the overall coal production in China. This area has become a major coal production area of China. However, the energy “Golden Triangle” region in western China has a fragile ecosystem. This region is exceptionally dry with scare and the water resource thereof is unevenly distributed, by location and season. For instance, the northern part of Shaanxi province is an inland area with little rainfall and high evaporation, and its per capita water resource is merely 927 m3, accounting for 35.7% of the average water resource per capita in China. Therefore, the northern part of Shaanxi province is a typical region with a severe water-shortage.
It is unavoidable that large-scale and intensive coal mining in this region will have negative impact on water resources in this region. The movement and storage state of surface and underground water can be affected by coal mine roadways and goafs, the circulation of the underground water has been changed, for example, dried-up river streams, decline of water table, and drastic decrease or drying up of spring-water. Water conservation, therefore, is recognized as the key to sustainable development in the energy “Golden Triangle” region. However, conventional water conservation technologies (such as backfill mining, height-limited mining) are not easy to implement in this region due to the constraint of the geological storage conditions of coal seams in this region. It is necessary to develop new technologies to protect and utilize water resource in this region. Currently, an important technology is to drain mine water. However, drainage of mine water has numerous disadvantages, one of which is to produce extreme waste of water resource, and another of which is to cause pollution produced by the mine water being drained to the ground surface. Moreover, because it is arid in the energy “Golden Triangle” region, evaporation occurs rapidly and most drained water will evaporate before it can be effectively utilized.
Therefore, the key challenge related to water-preserving mining in the energy “Golden Triangle” region is how to prevent the mine water being drained. Goafs formed by underground mining can be used to store mine water. If this storage is supplemented by engineering measures for storing mine water resources, the stored water can be utilized by drilling holes, which connect the reservoirs to the ground surface. If so, the water resources can be used effectively in the future. Multiple goafs for storing water are communicated with each other through coal mine roadways or pipes, so as to form a communicated underground space for storing water, i.e., a distributed coal mine underground reservoir. Dam-constructing is important for the distributed coal mine underground reservoir and ensures the safety of water storage. Meanwhile, by constructing an artificial dam, the multiple goafs are connecting and thus constituted a greater water storage space. By taking advantage of the height difference between the goafs, free flow of the mine water in the reservoir and purifying of the mine water are achieved.
Currently, there are no references on building an artificial dam of distributed coal mine underground reservoir. Some regulations in China, e.g. “Safety Regulations in Coal Mine” and “Provisions on Prevention and Control of Water in Coal Mines”, prescribe constructing of sluice gates and sluice walls. But, these regulations mainly focus on prevention and control of water disaster, and do not relate to the underground reservoir storing water. In aspect of water conservancy project, the regulations in China prescribe, in detail, the dam-building of a ground surface reservoir which is substantially different from that of an underground reservoir. Therefore, it is of great significance for constructing an artificial dam for distributed coal mine underground reservoir.